While there is no definitive proof that Florence Nightingale was a lesbian, there are indeed plenty of historians who believe the hero of battlefield medicine and triage was probably attracted to women yet sublimated her sexuality in service to humanity.
Though 90 years separate their divergent analyses of the mother of modern nursing, two male historians each seem to judge Nightingale through their respective conclusions about her sexuality — or her supposed lack thereof.
Zeroing in on what he believes was Nightingale's contempt for the idea of marrying a man — she's reported to have turned down at least four such proposals — historian Lytton Strachey wrote in his survey of four notable figures of the 19th century, "It was very odd; what could be the matter with dear Flo? Mr. Nightingale suggested that a husband might be advisable; but the curious thing was that she seemed to take no interest in husbands."
On the other hand, and in the face of Nightingale's own letters expressing lover-like passions for and bed-sharing with women of all social ranking, there's author Mark Bostridge's 2008 biography of her. This account not only proclaims that Nightingale was straight but also declares she was really not even a nurse.
"She had a brief period in Germany before the Crimean War doing basic nursing training, and when she got to the Crimean War she did hardly any nursing at all, and never did any nursing subsequently," Bostridge said in an interview with The Independent. "So to think of her as a nurse is such a ridiculous thing. What she was is a great nursing theoretician."
Male historians' opinions about her personal life notwithstanding, there's not an argument to be made that the Lady With the Lamp saved countless lives in her time and beyond because of her revolutionary nursing and battlefield-medicine acumen based on hygiene, empirical evidence, and bringing humanity to the healing arts.